1. Field of the Invention
The present invention relates to window glazing fasteners and more particularly to strip-type fasteners adapted for attachment to existing window frames for securing auxiliary glazing sheets at their edge.
2. Description of the Prior Art
The advantages of double glazed windows in conserving heat have long been recognized. Buildings constructed in cold climates are usually provided with permanent double-paned windows or with removable storm windows. However, many older buildings are not so equipped. In addition, with the fast rising costs of energy, it has been recognized that significant savings can be realized in heating buildings in milder climates as well. It has also been recognized that cooling costs can be reduced by using multiple pane windows.
However, the costs of retrofitting older buildings with double paned windows or with conventional storm windows is often prohibitive, forcing the owners of such buildings to seek cheaper alternatives. Conventional storm windows are also heavy and susceptible to damage during handling and storage. The alternatives most commonly used include flexible vinyl plastic or mylar films, or rigid transparent plastic panes.
Numerous types of fasteners have been designed for mounting either flexible or rigid glazings to existing window panes. Such fasteners have met varying degrees of success. One very difficult problem that has been encountered in the mounting of flexible glazing films has been to stretch the films sufficiently to obtain a wrinkle free fit. It was quickly discovered that simply nailing wooden slats around the window frame to secure the edges of plastic film was unsatisfactory.
Various types of framing strips and bead strips have been suggested for securing the edges of the film along opposite sides of a window opening. Framing strips commonly have a groove or channel for receiving a complementary shaped bead strip to secure an edge portion of the flexible film within the channel. Such an arrangement is shown in my own prior patent, U.S. Pat. No. 3,991,806 and patents cited therein. However, such fasteners either fail to stretch the fabric sufficiently to remove the wrinkles when assembled, or are unable to hold the film under sufficient tension without the bead strips pulling out of their grooves. It would be preferable if such fasteners were capable of progressively stretching the flexible film sufficiently, as the auxiliary window is being assembled, to eliminate wrinkles. In addition, it would be preferable if such fastener were capable of holding the film in place without the bead strip pulling out of the groove when the film is fully stretched.
Another problem which arises in the use of mylar type glazing films in windows is that they rattle when buffeted by gusts of wind. The principle cause of such noise is that the glazing fasteners used to date hold the film too rigidly around its edges. It would be preferable if such fasteners included some means of damping out the vibrations of such films.
Another problem is that the previous glazing fasteners have tended to be specialized for a single purpose, either for holding a rigid glazing sheet, or for holding a flexible glazing sheet, but not both. Glazing fasteners designed to secure rigid glazing sheets are disclosed in the designs of Toth, U.S. Pat. No. 2,701,041; DiLemme, U.S. Pat. No. 3,020,605; Migneault et al, U.S. Pat. No. 3,144,689; and Frank et al, U.S. Pat. No. 3,668,830. In such designs an external flange typically presses the rigid glazing against the window frame. Thus, they are designed to resist forces tending to push the glazing outwardly from the window. If such fasteners were used to secure flexible films under tension, the beads would be easily pulled from the channels. It would be preferable for the external flange, the channel and the insert portion or bead of the glazing strip to cooperate to resist both the outward forces of a rigid window glazing and the inward tension stretched flexible film glazings.
The previous flexible glazing fasteners are either unsatisfactory for stretching and holding a flexible film wrinkle-free across a window opening, or are incapable of also securing a rigid glazing. In the design of Lewis et al, U.S. Pat. No. 3,143,165, the glazing strip has an external flange extending laterally from the upper portion of the insert bead which might also be useful for securing a rigid window pane. However, that design employs only a single-lobed bead and is therefore incapable of progressively stretching flexible film adequately to obtain a wrinkle-free fit.
In U.S. Pat. No. 2,496,910, Fridolph discloses several glazing strip assemblies designed for securing the edge of fabric covering a surface. However, none of these assemblies appears to be adapted to stretching and holding a flexible glazing sheet under tension.
One such fastener employs a base strip with a channel and a capping strip with a flange portion designed for insertion into the channel together with the edge of the fabric. The flange has two longitudinal ribs along each side and the channel has a lip on each side of its entrance, but the channel is wider than it is deep, and the cross-sectional length of the ribbed flange is approximately equal to its width. Thus, although such assembly may be satisfactory for containing a margin of unstretched fabric, it would neither stretch a flexible glazing sheet adequately nor hold it in place once stretch without the capping strip being pulled from the channel. Preferably the insert flange would be longer and the channel deeper to stretch the glazing material more tightly when the glazing strip is applied. It would also be preferable for the channel to be relatively narrower over its entire length so as to obtain better frictional engagement between the surfaces of the channel and the flange. Finally, it would be preferable for the channel to have a second rib for mechanically engaging between the two ribs on at least one side of the insert flange.
Fridolph discloses another glazing fastener which employs a capping strip and a base strip each having a semicircular channel and a flange. The flanges of each strip are rounded and positioned for insertion into the channel in the opposite strip together with the edge of the fabric. The capping strip also has a laterally extending flange for holding the fabric against the surface. Again, it is unlikely that such assembly would withstand significant tension placed on the fabric. Stretching the fabric would tend to lift the laterally extending flange causing the relatively short insert flanges to be pulled from their respective channels. It would be preferable to have a glazing fastener arranged so that such tension could be translated into a force that would cause the surfaces of the flange and channel to interengage more tightly, rather than pulling the insert flange from its channel. It would be better still if such forces would cause ribs on the flange to interlock more tightly with ribs on the channel walls.
Previously glazing fasteners typically rely on the structural rigidity of the frame or sash to which they are attached to maintain their shape. They are neither sufficiently rigid to be used as stand-alone frames, nor able to be connected together to form the corners of such frames. It would be preferable to have a glazing strip which can either be attached to existing frames or used as an independent storm window frame. It would also be preferable to have a sliding sash storm window which can be opened independently of the existing sash. Finally, it would be preferable to have a light weight, inexpensive storm window which is easily adapted to fit within spaces provided in existing window frames for conventional storm windows or window screens.